Reduced Stiffness Microstructure for MEMS Switches
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Solution Overview
Problem
MEMS and MOEMS devices face limitations due to the use of positive stiffness elements, which require high actuation voltages and lead to stiction issues and increased power demands, especially in capacitive and ohmic switches.
Innovation Solution
A zero or near-zero stiffness micro-mechanical structure is created using a pair of buckled membranes, allowing for a reduced stiffness microstructure that transitions through zero stiffness zones, enabling lower actuation voltages and reduced stiction by utilizing buckled membranes with tailored properties and materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If positive stiffness elements are used in MEMS switches, then the switch can overcome stiction and maintain reliability, but high actuation voltages are required and power consumption increases
Solution Approach 1:
The patent changes the stiffness parameter from positive to near-zero by introducing pre-compression forces through buckled membranes. This parameter transformation allows the switch to overcome stiction with minimal actuation voltage, resolving the contradiction between reliability and power consumption.
Solution Approach 2:
The patent replaces traditional positive stiffness mechanical elements with a near-zero stiffness system using buckled membranes. This substitution fundamentally changes the mechanical behavior from high-restoring-force to low-restoring-force, enabling operation at much lower voltages while maintaining switch reliability.
2Duration of action of moving object
If high stiffness cantilevers are used in ohmic MEMS switches, then the switch can maintain reasonable lifetime by overcoming stiction, but even larger actuation voltages are required
Solution Approach 1:
The patent transforms the stiffness parameter from high (traditional cantilevers) to near-zero (buckled membrane system). This parameter change reduces the actuation force requirement while maintaining the restoring force necessary for switch lifetime, resolving the contradiction between lifetime and actuation voltage.
Solution Approach 2:
The patent uses composite structures combining buckled membranes with controlled pre-compression forces. This composite approach creates a near-zero stiffness system that provides both low actuation requirements and sufficient restoring force for reliable operation over extended lifetimes.
3Device complexity
If traditional positive stiffness elements are used, then structural simplicity is maintained, but device functionality is limited
Solution Approach 1:
The patent introduces dynamic control of stiffness through the buckled membrane system. By controlling the pre-compression force, the system can transition between different stiffness states, enabling versatile functionality while maintaining relatively simple structural implementation.
Solution Approach 2:
The near-zero stiffness buckled membrane system serves multiple functions: it provides low actuation for switch operation, maintains reliability through controlled restoring forces, and enables extended lifetime for ohmic contacts. This multi-functional approach enhances device versatility without significantly increasing structural complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the power requirements and stiction in MEMS and MOEMS devices, enabling lower maintaining voltages and extending switch lifetime by utilizing buckled membranes with tailored force-displacement characteristics.
Implementation Method 1
a zero or near-zero stiffness micro-mechanical structure is created using a pair of buckled membranes
Data Source
AI summary
Methods are described to create a reduced stiffness microstructure (RSM). A RSM is made by forming a first buckled membrane along a first buckling direction and forming a second buckled membrane along a second buckling direction. The second buckling direction is opposite to the first buckling direction and the first buckled membrane is in contact with the second buckled membrane over a contact area. Within an operating zone, a stiffness of the reduced stiffness microstructure during contact is less than an absolute value of a stiffness of at least one of the first buckled membrane, before contact, and the second buckled membrane, before contact, when the contact area translates along either one of the first buckling direction and the second buckling direction. In the operating zone the stiffness can approach or equal zero.